In the coming year studies of food iron availability will be continued. The conditions required for absorption of food in the duodenum will be examined and the intracellular chemistry of iron transport will be studied. The effects of iron deficiency will be examined. A search will be made for a more suitable animal in which to produce parenchymal iron overload. The differences in behavior of the two iron binding sites in transferrin, and their effects, if any, on current ferrokinetic models of internal iron distribution will be studied. The problem of differentiating cell sequestration from cell breakdown in sickle cell anemia will be worked on. Granulocyte kinetics will be examined in patients with leukopenia and leukocytosis by techniques which will permit a quantitative evaluation of total and effective granulocyte production. The role of the spleen in the production of leukopenia will be examined with these techniques in the experimental animal and in man.